Effect of Nb-doping on the MnFeOx catalyst for NH3-SCR reaction at low-temperature

BACKGROUND

Manganese-based catalysts were considered the most promising catalysts for low-temperature selective catalytic reduction (NH₃-SCR) reactions. In this work, a series of Mn₃Fe₂Nb_yO_x catalysts were synthesized by co-precipitation method for low-temperature NH₃-SCR and SO₂ tolerance tests.

RESULTS

The catalysts were characterized by BET, SEM, XRD, XPS, H₂-TPR, and NH₃-TPD. Mn₃Fe₂Nb_0.01O_x exhibited exceptionally high activity with a conversion of almost 100% from 80°C to 240°C, and a NO conversion of more than 75% at 40°C, while the NO conversion at 140°C in the presence of 100 ppm SO₂ remained above 90% for 4 h.

CONCLUSION

According to the characterization results, Nb modification can expand the specific surface area of the catalyst, improve the structure of the catalyst, and make the active components on the catalyst surface more dispersed. Moreover, the Nb-modified catalyst reduced the content of Mn²⁺ on the catalyst surface and strengthened the electronic interactions between elements. The synergistic effects among Mn, Fe, and Nb facilitate the formation of more chemically adsorbed oxygen, which enhances the reduction capacity of the catalyst. This facilitates the adsorption of NH₃ by the catalyst at low temperatures and promotes the process of low-temperature NH₃-SCR reaction. More importantly, the Nb-modified catalyst possessed more weak acid sites, and the higher surface acidity was conducive to the inhibition of SO₃ generation, which enhanced the sulfur poisoning resistance of the catalyst. © 2024 Society of Chemical Industry (SCI).